U.S. patent application number 15/298550 was filed with the patent office on 2017-04-20 for gas ejection duct with acoustic treatment, an aircraft, and a method of fabricating such a duct.
This patent application is currently assigned to AIRBUS HELICOPTERS. The applicant listed for this patent is AIRBUS HELICOPTERS. Invention is credited to Remi HERFORT, Philippe LOEWENSTEIN.
Application Number | 20170107909 15/298550 |
Document ID | / |
Family ID | 54937146 |
Filed Date | 2017-04-20 |
United States Patent
Application |
20170107909 |
Kind Code |
A1 |
LOEWENSTEIN; Philippe ; et
al. |
April 20, 2017 |
GAS EJECTION DUCT WITH ACOUSTIC TREATMENT, AN AIRCRAFT, AND A
METHOD OF FABRICATING SUCH A DUCT
Abstract
A gas ejection duct with acoustic treatment provided with at
least one wall referred to as an "acoustic" wall for coming into
contact with the gas. The acoustic wall comprises an inner skin and
an outer skin that are spaced apart at least in part by a space,
the acoustic wall including at least one internal mesh in the
space, the mesh defining a plurality of cavities. Each cavity has
the shape of a parallelepiped, each mesh extending longitudinally
in a direction referred to as the "fabrication" direction that
presents an acute angle greater than or equal to a predetermined
angle relative to a horizontal plane, each of the inner and outer
skins presenting an acute angle of inclination greater than or
equal to the at least one predetermined angle relative to the
horizontal plane.
Inventors: |
LOEWENSTEIN; Philippe;
(Sausset Les Pins, FR) ; HERFORT; Remi;
(Verneuil-sur-Seine, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AIRBUS HELICOPTERS |
Marignane |
|
FR |
|
|
Assignee: |
AIRBUS HELICOPTERS
Marignane
FR
|
Family ID: |
54937146 |
Appl. No.: |
15/298550 |
Filed: |
October 20, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F05D 2260/963 20130101;
C22C 19/056 20130101; B33Y 80/00 20141201; G10K 11/161 20130101;
B22F 3/1055 20130101; B64D 33/06 20130101; F01D 25/005 20130101;
B33Y 10/00 20141201; F02C 7/24 20130101; Y02T 50/60 20130101; Y02T
50/671 20130101; F01D 25/30 20130101; F02K 1/827 20130101; F05D
2220/32 20130101 |
International
Class: |
F02C 7/24 20060101
F02C007/24; F01D 25/00 20060101 F01D025/00; C22C 19/05 20060101
C22C019/05; B22F 3/105 20060101 B22F003/105; B33Y 10/00 20060101
B33Y010/00; B33Y 80/00 20060101 B33Y080/00; F01D 25/30 20060101
F01D025/30; G10K 11/16 20060101 G10K011/16 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 20, 2015 |
FR |
1502204 |
Claims
1. A gas ejection duct with acoustic treatment that is provided
with at least one mechanical member, the mechanical member having
at least one wall referred to as an "acoustic" wall for coming into
contact with the gas, the acoustic wall having an inner skin and an
outer skin that are spaced apart at least in part by a space, the
acoustic wall including at least one internal mesh arranged in the
space, the mesh defining a plurality of cavities, each cavity
extending in the thickness direction from the inner skin to the
outer skin, the inner skin being for coming into contact with the
gas, the inner skin having perforations, each cavity communicating
with at least one perforation, wherein each cavity is of
parallelepiped shape, each cavity being defined in elevation by a
partition referred to as "top" partition and a partition referred
to as a "bottom" partition, each cavity being defined transversely
by a partition referred to as a "left side" partition and a
partition referred to as a "right side" partition which are
extending in elevation from the bottom partition to the top
partition, each cavity being defined transversely in thickness by a
non-perforated portion of the outer skin and a perforated portion
of the inner skin, at least one of the partitions of a cavity
presenting a drain opening opening out to outside the cavity.
2. A gas ejection duct with acoustic treatment according to claim
1, wherein the gas ejection duct with acoustic treatment extends in
elevation from a base to a top, the inner wall and the outer wall
and each mesh extend in elevation relative to a fabrication plane
referred to as the "horizontal" plane that is tangential to the
base, each mesh extends in elevation in a direction referred to as
the "fabrication direction" presenting an acute angle greater than
or equal to a predetermined angle relative to the horizontal plane,
and each of the inner and outer walls presents an acute angle of
inclination relative to the horizontal plane that is greater than
or equal to the predetermined angle.
3. A gas ejection gas duct with acoustic treatment according to
claim 2, wherein the predetermined angle is equal to 45
degrees.
4. A gas ejection gas duct with acoustic treatment according to
claim 2, wherein each tangent to either one of the inner and outer
skins that is arranged in a plane perpendicular to the horizontal
plane presents a said angle of inclination.
5. A gas ejection duct with acoustic treatment according to claim
1, wherein the cavities of a mesh are arranged in elevation (Z) one
above another, and transversely (Y) one beside another.
6. A gas ejection duct with acoustic treatment according to claim
1, wherein each of the partitions is rectangular.
7. A gas ejection duct with acoustic treatment according to claim
1, wherein each cavity has the shape of a non-rectangular
parallelepiped, each of the bottom and top partitions presenting an
acute angle not equal to 90 degrees relative to the left side
partition or the right side partition.
8. A gas ejection duct with acoustic treatment according to claim
1, wherein the acoustic wall is made out of the NiCr19Fe19Nb5Mo3
material.
9. A gas ejection duct with acoustic treatment according to claim
1, wherein at least one of the inner and outer walls presents a
thickness (ep) less than one millimeter.
10. A gas ejection duct with acoustic treatment according to claim
1, wherein each perforation presents a diameter less than or equal
to four millimeters.
11. A gas ejection duct with acoustic treatment according to claim
1, wherein each cavity communicates with at least four perforations
with a maximum diameter of 1.5 millimeters.
12. A gas ejection duct with acoustic treatment according to claim
1, wherein the gas ejection duct with acoustic treatment is a
nozzle and each mechanical member is selected from a list
comprising a skirt, a central cone, and an arm connecting the skirt
to the central cone.
13. A gas ejection duct with acoustic treatment according to claim
1, wherein the gas ejection duct with acoustic treatment includes
at least one skin having at least one drainage orifice.
14. An aircraft provided with a gas ejection duct with acoustic
treatment, wherein the gas ejection duct with acoustic treatment is
according to claim 1.
15. A method of fabricating a gas ejection duct with acoustic
treatment according to claim 1, wherein the gas ejection duct with
acoustic treatment is made by performing a laser sintering method,
the gas ejection duct with acoustic treatment being built up layer
by layer by repeating the following steps: using a roller to
deposit a layer of material; locally consolidating the layer; and
lowering a tray supporting the gas ejection duct with acoustic
treatment that is being fabricated.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to French patent
application No. FR 15 02204 filed on Oct. 20, 2015, the disclosure
of which is incorporated in its entirety by reference herein.
BACKGROUND OF THE INVENTION
[0002] (1) Field of the Invention
[0003] The present invention relates to a gas ejection duct with
acoustic treatment, and to an aircraft having such a duct. The
invention also relates to a method of fabricating such a duct.
[0004] The invention lies in the technical field of gas ejection
ducts for aircraft.
[0005] (2) Description of Related Art
[0006] An aircraft usually has an engine contributing to providing
the aircraft with propulsion or indeed lift. For example, a
rotorcraft may have a fuel burning engine that rotates a rotor
contributing at least to providing the aircraft with lift.
[0007] The engine generates exhaust gas that is expelled out from
the aircraft by an ejection system. On an aircraft, a gas ejection
system may include a duct commonly referred to as a "nozzle" for
discharging exhaust gas out from the aircraft. An engine may also
include a gas takeoff duct taking gas to other equipment of the
aircraft.
[0008] The engines used in aviation can produce noise that is
painful for a human to hear. Gas ejection systems are therefore
sometimes acoustically treated in an attempt to reduce the noise
they emit, in particular in a frequency range that is painful to
hear for the human ear.
[0009] The gas ejection systems of aircraft also need to satisfy
mechanical strength requirements relating to the surrounding
environment and to satisfy the requirements of official aviation
regulatory agencies.
[0010] In order to reduce emitted noise, a mechanical system may
have walls provided with small cells that are locally open to the
outside and that form so-called "Helmholtz" resonators. Such cells
are referred to as "cavities" for convenience.
[0011] Helmholtz resonance is a physical phenomenon that appears
when a sound wave travels close to a cavity in communication with
the outside via an opening. The original sound wave penetrates into
the cavity through the opening, and is then reflected inside the
cavity so as to form a wave that is phase shifted, while remaining
an image of the original acoustic wave. The original acoustic wave,
when superposed on the phase shifted wave, leads to a resulting
wave that is attenuated. The level of sound emission is thus
decreased.
[0012] Such cavities therefore operate in the presence of acoustic
waves such as a vibrating system having one degree of freedom with
its mass associated with the dimensions of the cavities, with its
stiffness associated with the volume of air in each cavity, and
with its damping associated with the resistance opposed by the
outside medium to generating acoustic waves.
[0013] On an aircraft, a wall provided with resonators making use
of this principle has a core defining small cavities of hexagonal
section in application of the principle of the Helmholtz resonator.
Such a cavity is then in the form of a prism of hexagonal section
extending in elevation from an open base towards an open top. Given
this shape, the core is referred to as a "honeycomb" layer.
[0014] The core is then brazed to a rear metal sheet that closes
the base of each prism. Furthermore, a perforated skin rests on the
tops of the prism so that each cavity can communicate via a
plurality of perforations with the ejected gas.
[0015] Thus, a helicopter gas ejection prototype with acoustic
treatment includes sheets made of titanium. Sheets are shaped and
welded together to form a wall having cavities of hexagonal section
or cavities of large dimensions. The wall also has a perforated
skin attached to the cavities.
[0016] That gas ejection prototype provides cavities presenting
dimensions that are different. As a result, the use of cavities
with different volumes serves to attenuate noise over a wider
frequency range. Nevertheless, making different cavities turns out
to be difficult when using metal sheets that are brazed to one
another.
[0017] In addition, assembling sheets requires numerous fabrication
operations. In particular, such assembly can require fine metal
sheets to be brazed together, which is difficult.
[0018] Consequently, making a gas ejection duct, and in particular
a nozzle, that is provided with such acoustic treatment means can
be difficult and/or expensive.
[0019] Documents FR 2 712 640, FR 2 929 336, and EP 2 865 947 are
remote from the problem of the invention and are mentioned purely
by way of information.
[0020] Document FR 2 712 640 describes a structure having a surface
with low aerodynamic drag. That structure has cells opening out to
an outside medium via one opening and to a channel via another
opening.
[0021] Document FR 2 929 336 relates to a device having plane jets
used to reduce the noise generated by an aircraft jet engine. The
device has a wall surrounding a stream of gas ejected by a jet
engine. Ducts are distributed at a periphery of a downstream end of
the wall in order to eject a jet of fluid in the form of a
sheet.
[0022] Document EP 2 865 947 provides a damper in order to reduce
acoustic pulsations in a gas turbine chamber. That damper has a
cavity opening out to a bent tube in communication with the
chamber.
[0023] Documents EP 1 998 003, U.S. Pat. No. 4,240,252, U.S. Pat.
No. 4,452,335, WO 2015/098148, and EP 1 391 597 are also known.
BRIEF SUMMARY OF THE INVENTION
[0024] An object of the present invention is thus to provide a gas
ejection duct with acoustic treatment that presents a structure
capable of enabling it to be made in optimized manner.
[0025] According to the invention, a gas ejection duct with
acoustic treatment is provided with at least one mechanical member,
the mechanical member having at least one wall referred to as an
"acoustic" wall for coming into contact with the gas, the acoustic
wall having an inner skin and an outer skin that are spaced apart
at least in part by a space, the acoustic wall including at least
one internal mesh arranged in the space, the mesh defining a
plurality of cavities, each cavity extending in the thickness
direction from the inner skin to the outer skin, the inner skin
being for coming into contact with the gas, the inner skin having
perforations, each cavity communicating with at least one
perforation.
[0026] The gas ejection duct with acoustic treatment may be a
nozzle directing the gas to the outside of the aircraft, or it may
be a takeoff pipe directing gas to at least one other piece of
equipment of an aircraft.
[0027] Each cavity is in the shape of a parallelepiped.
[0028] In a variant, seeking to optimize fabrication of the duct,
the gas ejection duct with acoustic treatment extends in elevation
from a base to a top, the inner wall and the outer wall and each
mesh extend in elevation relative to a fabrication plane referred
to as the "horizontal" plane that is tangential to the base, each
mesh may extend in elevation in a direction referred to as the
"fabrication direction" presenting an acute angle greater than or
equal to a predetermined angle relative to the horizontal plane,
and each of the inner and outer walls may present an acute angle of
inclination relative to the horizontal plane that is greater than
or equal to the predetermined angle.
[0029] The term "each presenting an angle of inclination" means
that each surface of each member in question presents the specified
angle of inclination.
[0030] The term "in elevation" refers to a direction that presents
an acute or zero angle relative to gravity during fabrication of
the wall in question.
[0031] Consequently, the term "longitudinal" refers to a direction
which a cavity extends going from the bottom skin towards the top
skin. The term "transverse" refers to a direction substantially
orthogonal to a direction in elevation and to a longitudinal
direction.
[0032] Consequently, the gas ejection duct with acoustic treatment
may be made in accordance with the invention by performing a laser
sintering method, said gas ejection duct with acoustic treatment
being made in elevation layer by layer from a base towards a top by
repeating the fowling steps:
[0033] using a roller to deposit a layer of material such as a
metal powder;
[0034] consolidating said layer locally, by using a laser; and
[0035] lowering a tray supporting the gas ejection duct acoustic
treatment being fabricated in order to deposit the following
layer.
[0036] When the gas ejection duct with acoustic treatment has been
finished, the gas ejection duct with acoustic treatment is
extracted from the fabrication device in order to remove the powder
that surrounds it.
[0037] Three-dimensional printing technology, and in particular
sintering a powder with a laser, is advantageous because of its
relative simplicity. This technology enables parts of relatively
complex shape to be made with fabrication costs that are
reasonable.
[0038] Nevertheless, this technology is not always easy to
implement.
[0039] Thus, in the present invention, an acoustic wall of a gas
ejection duct with acoustic treatment presents Helmholtz resonators
that are in the shape of parallelepipeds and that are not of
honeycomb shape. This innovative parallelepiped shape enables the
mesh to be fabricated in elevation and avoids using surfaces that
are substantially horizontal, which surfaces are impossible to
fabricate with a laser sintering method. This parallelepiped shape
also optimizes the acoustically treated surface by enabling an
unlimited number of cavities to be aligned transversely and in
elevation without loss of treated surface area.
[0040] In addition, the parallelepiped shape can be used to
attenuate soundwaves that are very painful to hear for the human
ear, at a frequency close to 5000 hertz (Hz).
[0041] In addition, the cavities of a mesh lie in a plane that
extends transversely and in elevation, presenting an acute angle
greater than or equal to a predetermined angle relative to a
horizontal plane.
[0042] Specifically, the Applicant has observed that a wall
presenting an angle that is too small relative to a horizontal
plane cannot be fabricated by laser sintering. Specifically, such
an angle does not enable the powder of a layer to be kept supported
on the preceding layer.
[0043] Consequently, the other elements of the gas ejection duct
with acoustic treatment and in particular the inner skin and the
outer skin of an acoustic wall also present an angle of inclination
that is acute, being greater than or equal to said predetermined
angle.
[0044] Furthermore, the gas ejection duct with acoustic treatment
can be made by laser sintering using a strong metal material.
[0045] In addition, fabrication of an article by laser sintering
requires the removal of powder residue, and that presents a problem
in the presence of cavities. The perforations in the inner skin can
nevertheless contribute to removing residue of the powder that has
been used for fabrication, and can also serve to drain the gas
ejection duct with acoustic treatment.
[0046] Consequently, the gas ejection duct with acoustic treatment
can satisfy acoustic requirements because of the presence of
innovative cavities, can satisfy the requirements of regulatory
agencies (drainage, mechanical strength, . . . ), can satisfy the
requirements necessary for the mechanical strength of the gas
ejection duct with acoustic treatment in given environment
conditions (temperature, pressure, . . . ), and finally can satisfy
design requirements for laser sintering a metal powder (skin
thicknesses, angles relative to the vertical, . . . ).
[0047] The gas ejection duct with acoustic treatment may also
include one or more of the following characteristics.
[0048] Thus, the determined angle may optionally be equal to 45
degrees.
[0049] In addition, each tangent to either one of said skins that
is arranged in a plane perpendicular to the horizontal plane
presents a said angle of inclination.
[0050] Consequently, each surface of the walls present the required
angle of inclination.
[0051] Furthermore, and by way of example, said cavities of a mesh
are arranged in elevation one above another, and transversely one
beside another.
[0052] The mesh is in the form of a plane of thickness equal to the
thickness of the cavities in a longitudinal direction. This
arrangement enables the mesh to be made easily by laser
sintering.
[0053] In addition, each cavity is defined in elevation by a
partition referred to as "top" partition and a partition referred
to as a "bottom" partition, each cavity being defined transversely
by a partition referred to as a "left side" partition and a
partition referred to as a "right side" partition, each extending
in elevation from the bottom partition to the top partition, each
cavity being defined transversely in thickness by a non-perforated
portion of the outer skin and a perforated portion of the inner
skin.
[0054] Each cavity is then defined by six faces, namely a top
partition substantially parallel to a bottom partition, a left side
partition substantially parallel to a right side partition, and a
front non-perforated portion of the outer skin substantially
parallel to a rear perforated portion of the inner skin.
[0055] Each of said partitions is optionally rectangular.
[0056] Furthermore, each cavity may have the shape of a
non-rectangular parallelepiped, each of the bottom and top
partitions presenting an angle not equal to 90 degrees relative to
the left side partition or the right side partition.
[0057] In contrast, and like the mesh and also the inner and outer
skins, each partition presents an angle lying in the range 45
degrees to 90 degrees relative to a horizontal plane.
[0058] In addition, at least one said partition of a cavity
presents a drain opening opening out to the outside of the
cavity.
[0059] The gas ejection duct with acoustic treatment thus contains
openings enabling the gas ejection duct with acoustic treatment to
be drained.
[0060] In particular, each cavity can communicate with each
transversely adjacent cavity via an opening to enable powder to
escape after fabrication. Two transversely adjacent cavities thus
share a common side wall, the left side wall of one cavity
representing the right side wall of the other cavity. The side wall
may then present a drain opening.
[0061] This characteristic is not obvious in the context of
applying the Helmholtz principle. Nevertheless, the Applicant has
found that a side partition with a limited opening still enables a
cavity to be obtained that presents good acoustic performance.
[0062] Likewise, the gas ejection duct with acoustic treatment may
include at least one skin having at least one drain orifice opening
out to the outside of the gas ejection duct with acoustic
treatment.
[0063] The gas ejection duct with acoustic treatment then contains
internal holes of the drainage orifice type that makes drainage
possible. For example, the space present between an inside skin and
an outside skin leads to at least one drainage orifice provided in
the inside skin or the outside skin.
[0064] In addition, the acoustic wall may be made out of a variety
of materials, and in particular out of materials compatible with
the laser sintering method, which is also known as additive layer
manufacturing (ALM).
[0065] It is possible to use titanium 6242.
[0066] Likewise, the acoustic wall may be made out of the
NiCr19Fe19Nb5Mo3 material.
[0067] This material corresponds to a material known under the
trademark Inconel 718. The material used for fabricating the gas
ejection duct with acoustic treatment may thus be Inconel 718
powder, thus making it possible to satisfy requirements for
mechanical strength in the external environment around the gas
ejection duct with acoustic treatment while using thicknesses that
are small.
[0068] Thus, at least one of said inner and outer walls may present
thickness of less than one millimeter.
[0069] The term "thickness" represents the smallest dimension of a
skin.
[0070] Furthermore, each perforation may be present a diameter that
is less than or equal to four millimeters, and that is of
millimeter order.
[0071] Likewise, the above-described openings and orifices
optionally present a diameter less than or equal to four
millimeters.
[0072] The Applicant has found that making a hole having a diameter
greater than four millimeters in a plane that extends in elevation
is difficult if not impossible.
[0073] Consequently, each cavity optionally communicates with at
least four perforations having a maximum diameter of 1.5
millimeters.
[0074] The cavities are covered in a perforated inner skin having
perforations with a diameter of 1.5 millimeters so as to enable a
Helmholtz resonance phenomenon to occur at a calculated frequency
of 5000 Hz. This frequency is determined on the basis of the volume
of the cavities, of the speed of sound, and of the number and the
diameter and the depth of the perforations.
[0075] In addition, the gas ejection duct with acoustic treatment
may be a nozzle, each mechanical member being selected from a list
comprising a skirt, a central cone, and an arm connecting said
skirt to the central cone.
[0076] By way of example, the gas ejection duct with acoustic
treatment may be made on the basis of the Tigre.RTM. helicopter
nozzle by incorporating acoustic walls of the invention in the
skirt, in the central cone, and in the arms of the nozzle.
[0077] Furthermore, the invention provides an aircraft having a gas
ejection duct with acoustic treatment of the type described
above.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0078] The invention and its advantages appear in greater detail
from the context of the following description of embodiments given
by way of illustration and with reference to the accompanying
figures, in which:
[0079] FIG. 1 is a view of an aircraft of the invention;
[0080] FIG. 2 is a three-dimensional view of a gas ejection duct
with acoustic treatment of the type comprising a gas ejection
nozzle with acoustic treatment;
[0081] FIG. 3 is a view of a portion of an acoustic wall;
[0082] FIG. 4 is a view explaining the inclination and the angle
that are authorized for the inner and outer skins, and also for the
mesh;
[0083] FIG. 5 is an exploded view of a portion of an acoustic wall
showing cavities;
[0084] FIG. 6 is a view of a skirt for a gas ejection duct with
acoustic treatment of the type comprising a gas ejection nozzle of
the invention with acoustic treatment of the invention;
[0085] FIG. 7 is a view of an arm of a gas ejection duct with
acoustic treatment of the type comprising a gas ejection nozzle
with acoustic treatment;
[0086] FIGS. 8 and 9 show a central cone of a gas ejection duct
with acoustic treatment of the type comprising a gas ejection
nozzle with acoustic treatment;
[0087] FIG. 10 is a view of a gas ejection duct with acoustic
treatment of the type including a gas takeoff duct; and
[0088] FIG. 11 is a view of a fabrication device illustrating the
method of the invention.
[0089] Elements present in more than one of the figures are given
the same references in each of them.
DETAILED DESCRIPTION OF THE INVENTION
[0090] It should be observed that three mutually orthogonal
directions X, Y, and Z are shown in some of the figures.
[0091] The direction X is said to be longitudinal. Another
direction Y is said to be transverse. Finally, a third direction Z
is said to be in elevation, and corresponds to the height
dimensions of the structures described.
[0092] FIG. 1 shows an aircraft 1 of the invention.
[0093] This aircraft 1 has a power plant 3 having at least one
engine 4. For example, the engine acts via a main gearbox 5 to
drive a rotor 2 that participates at least to providing the
aircraft with lift. The engine 4 may be a fuel burning engine
ejecting gas 200, such as piston engine or a turboshaft engine.
[0094] In order to discharge gas from the engine, the aircraft 1 is
provided with a gas ejection duct 8 with acoustic treatment.
[0095] Such a gas ejection duct 8 with acoustic treatment may be a
gas ejection nozzle 10 with acoustic treatment directing the gas
towards the outside of the aircraft, e.g. downstream from an
expansion turbine of a turboshaft engine.
[0096] In addition, a gas ejection duct 8 with acoustic treatment
may be in the form of a gas takeoff duct for taking off gas from
the engine 4 and directing the gas to at least one other piece of
equipment 6 of the aircraft, e.g. such as an air conditioning
system. For example, the gas is taken off from a gas generator of a
turboshaft engine.
[0097] The gas ejection duct 8 with acoustic treatment comprises at
least one mechanical member 11. This mechanical member 11 is
acoustically treated in order to reduce the emission of noise when
exhausting gas 200.
[0098] By way of example, the takeoff duct 9 has a bend 500
followed by a diffuser 502.
[0099] In addition and by way of example, the gas ejection nozzle
10 with acoustic treatment may be provided with a skirt 20. The
skirt 20 is provided with a diverging member 21 secured to a flange
22. The flange 22 may be bolted to the engine 4, for example. Such
a diverging member 21 may then represent an acoustically treated
mechanical member 11.
[0100] The gas ejection nozzle 10 with acoustic treatment is also
provided with a central cone 15 that may represent an acoustically
treated mechanical member 11. By way of example, the central cone
may comprise an outer converging member 16 that surrounds an inner
converging member 17. The inner converging member is then connected
to the base of the outer converging member 16.
[0101] In addition, the gas ejection nozzle 10 with acoustic
treatment is also provided with a plurality of arms 25, each
connecting the outer converging member 16 of the central cone 15 to
the diverging member 21 of the skirt 20. By way of example, at
least one arm 25 extends radially and may represent an acoustically
treated mechanical member 11.
[0102] FIG. 2 is a three-dimensional view of a gas ejection duct 8
with acoustic treatment comprising a gas ejection nozzle 10 with
acoustic treatment of the invention.
[0103] Independently of the nature of the gas ejection duct 8 with
acoustic treatment, each acoustically treated mechanical member
presents an innovative acoustic wall 30. Such an acoustic wall 30
has an outer skin 35 and an inner skin 40, the inner skin 40
necessarily facing a passage 201 through which the gas 200 passes.
This inner skin 40 presents perforations 41 for passing an acoustic
wave generated by the flow of gas 200.
[0104] The gas ejection duct 8 with acoustic treatment, and in
particular the acoustic wall 30, may be made out of the
NiCr19Fe19Nb5Mo3 material. Other materials may be envisaged.
[0105] FIG. 3 is a three-dimensional view of an acoustic wall
30.
[0106] As mentioned above, the acoustic wall 30 presents an outer
skin 35 and an inner skin 40.
[0107] The outer skin 35 and the inner skin 40 may locally form a
single common skin.
[0108] Nevertheless, the outer skin 35 and the inner skin 40 are
also spaced apart at least locally by an internal space 50. Under
such circumstances, a mesh 60 is arranged in this space 50.
[0109] The mesh 60 defines cavities that are not visible in FIG. 3,
each cavity representing a Helmholtz resonator. Under such
circumstances, each cavity communicates via perforations 41 with a
passage 201 passing the gas.
[0110] In order to enable the gas ejection duct 8 with acoustic
treatment to be fabricated from the bottom up by laser sintering,
the mesh 60 of an acoustic wall extends in elevation in a direction
referred to as the "fabrication" direction 301. This fabrication
direction 301 presents an acute angle 302 relative to a horizontal
plane 300 that is greater than or equal to a predetermined angle.
This horizontal plane represents the plane on which the first layer
of powder is deposited during fabrication.
[0111] Likewise, both the inner skin 40 and the outer skin 35
present an acute angle of inclination 303 relative to the
horizontal plane 300 that is greater than said predetermined
angle.
[0112] In general, and with reference to FIG. 4, every surface of
the gas ejection duct 8 with acoustic treatment extends upwards in
a direction that presents at least said predetermined angle with
the horizontal plane 300.
[0113] Specifically, when a layer of powder referred to as the
"higher" layer 411 is deposited on a layer referred to as the
"lower" layer 412, the higher layer 411 runs the risk of collapsing
under its own weight along arrow 413. Nevertheless, the Applicant
has observed that as from a predetermined angle, the higher layer
411 can remain on the lower layer 412.
[0114] By way of example, such a predetermined angle may be 45
degrees.
[0115] Under such circumstances, each of the outer and inner skins
35 and 40 has a tangent 401 arranged in a plane 400 that is
perpendicular to the horizontal plane 300. This tangent 401 then
presents an angle of inclination 303 relative to the horizontal
plane 300 that is greater than or equal to the predetermined
angle.
[0116] FIG. 5 is an exploded view of an acoustic wall 30 serving to
show the internal mesh 60.
[0117] The mesh 60 thus presents a plurality of cavities 61
extending transversely from the outer skin 35 towards the inner
skin 40.
[0118] Each cavity 61 is defined by six substantially plane
faces.
[0119] Thus, a cavity is defined in elevation in an elevation
direction Z firstly by a partition 62 referred to as the "top"
partition 63 and secondly by a partition 62 referred to as the
"bottom" partition 64. The top partition 63 is parallel to the
bottom partition 64.
[0120] In addition, the cavity 61 is defined transversely in a
transverse direction Y firstly by a partition 62 referred to as the
"left side" partition 65 and secondly by a partition 62 referred to
as the "right side" partition 66. The left side partition 65 is
parallel to the right side partition 66. In addition, each of the
left and right side partitions 65 and 66 extends upwards in
elevation in the wall fabrication direction from the bottom
partition 64 to the top partition 63.
[0121] Finally, each cavity 61 is defined longitudinally in
thickness in a longitudinal direction X firstly by a plane face
represented by a non-perforated portion 67 of the outer skin 35,
and secondly by a plane face represented by a perforated portion 68
of the inner skin 40.
[0122] By construction, each cavity then has an innovative
parallelepiped shape.
[0123] In particular, each partition may be rectangular.
[0124] Nevertheless, each cavity 61 may be in the form of a
non-rectangular parallelepiped. Both the bottom partition 64 and
the top partition 63 present an acute angle 304 that is not equal
to 90.degree. relative to the left side partition 65 or the right
side partition 66.
[0125] In addition, the cavities 61 of a mesh 60 are arranged in
elevation one above another, and transversely one beside
another.
[0126] Consequently, two transversely adjacent cavities 601 and 602
possess a common side partition 603.
[0127] Likewise, two cavities that are adjacent in elevation are
arranged one above the other. A cavity referred to as the "higher"
cavity 604 then lies above a cavity referred to as the "lower"
cavity 605. Under such circumstances, two adjacent cavities possess
a common partition 606 that constitutes a top partition for the
lower cavity 605 and a bottom partition for the higher cavity
604.
[0128] In addition, the left side partition of the higher cavity is
in alignment with the left side partition of the lower cavity, and
the right side partition of the higher cavity is situated in
alignment with the right side partition of the lower cavity. The
side partitions of a row of cavities arranged one above another
thus form a plane plate extending in elevation.
[0129] Furthermore, by construction, each cavity has an innovative
parallelepiped shape.
[0130] In order to enable powder residue to be removed during
fabrication of the acoustic wall, at least one partition 62 of a
cavity 61 has a drain opening 70 leading to outside the cavity
61.
[0131] For example, each side partition 65, 66 presents a drain
opening 70. The drain opening 70 then leads either to another
cavity or else to a portion of the space 50 that is not filled by a
mesh.
[0132] Likewise, at least one skin may be provided with at least
one drain orifice 71. Preferably, the outer skin of an acoustic
wall is provided with at least one drain orifice, the outer skin
not being in contact with the acoustic wave.
[0133] Furthermore, all of the holes formed in the gas ejection
duct 8 with acoustic treatment may be accurately dimensioned. These
holes include the above-described perforations, openings, and
orifices.
[0134] Thus, each perforation 41, and possibly each drain opening
and each drain orifice, presents a diameter 42 that is less than or
equal to 4 millimeters.
[0135] Specifically, the Applicant has observed that a larger
diameter can lead to induced sagging of a layer of powder during
fabrication by laser sintering.
[0136] Under such circumstances, each cavity may be in fluid flow
communication with a passage 201 passing the gas via four
perforations of diameter less than or equal to 1.5 millimeters.
[0137] Furthermore, the inner and outer skins 40 and 35 may be of
thicknesses that are small, while nevertheless being suitable for
being obtained by laser sintering. Under such circumstances, at
least one of the inner and outer skins 40 and 35 optionally
presents a thickness ep of less than one millimeter.
[0138] FIGS. 6 to 9 shows a gas ejection nozzle with acoustic
treatment of the invention that is provided with a skirt, a central
cone, and arms.
[0139] With reference to FIG. 6, the skirt 20 may comprise a
plurality a meshes 60 extending upwards in a fabrication direction
from a base 23 to a top 24.
[0140] The diverging member 21 of the skirt extends in a
fabrication direction upwards from a base 23 to a top 24. Between
the base 23 and its top 24, the diverging member 21 may have a
periodic shape forming folds. This periodic shape has a segment
that is repeated many times, the segment comprising in succession
an internal arch 211, a first side 212, an external arch 213, and a
second side 214. The internal arch 211 presents a convex face
facing an axis of symmetry AX of the diverging member 21, while the
external arch 213 presents a concave face facing the axis of
symmetry AX. Under such circumstances, the first side 212 extends
away from the axis of symmetry AX extending the internal arch 211
towards the external arch 213, while the second side 214 extends
towards the axis of symmetry AX, extending from the external arch
213.
[0141] Under such circumstances, at least one mesh 60 may be
arranged at the internal arch 211 at the first side 212, at the
external arch 213, and at the second side 214.
[0142] Furthermore, FIG. 6 shows the possibility of the outer skin
and the inner skin coming together locally, in particular at the
base 23 and/or at the top 24 of the diverging member 21.
[0143] FIG. 7 shows an arm 25 of the gas ejection nozzle 10 with
acoustic treatment. This arm extends upwards in a fabrication
direction from a foot 26 to an end 27, which foot 26 and end 27 may
be secured to the central cone 15 and to the skirt 20 of the gas
ejection nozzle 10 with acoustic treatment.
[0144] The arm may then have an acoustic wall 30 of the
above-described type.
[0145] FIGS. 8 and 9 show a central cone 15.
[0146] With reference to FIG. 9, the outer converging member 16 may
have an annular acoustic wall 30 of the invention.
[0147] The inner converging member 17 may possibly present only one
skin forming a cone that is open at its top. This skin presents the
required angle of inclination relative to the horizontal plane 300,
and possibly also at least one drain orifice 72.
[0148] FIG. 10 shows a takeoff duct 9 of the invention. The takeoff
duct 9 has a bend 500 followed by a diffuser 502. The bend 500
and/or the diffuser 502 may comprise acoustic walls 30 of the
above-described type.
[0149] Optionally, the bend 500 and/or the diffuser 502 are
fastened to a fastener flange 501.
[0150] FIG. 11 shows a device 100 for fabrication by laser
sintering that enables the method of the invention to be
performed.
[0151] The fabrication device 100 includes a table 101 or the
equivalent. The table 101 defines a well 102. The well 102 is open
at its top but it presents a bottom that is movable. The movable
bottom is obtained by means of a tray 110 that is movable in
elevation as represented by double-headed arrow 103.
[0152] Furthermore, the fabrication device 100 has a roller 104
rolling on the table 101 in the directions of double-headed arrow
105. The roller 104 enables successive layers of powder to be
deposited in the well 102.
[0153] Furthermore, the fabrication device 100 has a laser system
106 suitable for solidifying predetermined zones of the powder
deposited in the well. The laser system 106 then has at least one
laser emitter 107 emitting a laser beam. Furthermore, the laser
system 106 has an optical system 108 suitable for directing the
laser beam into the required zones.
[0154] The fabrication device 100 also possesses an electronic
system (not shown) for controlling the tray 110, the roller 104,
and the laser system 106.
[0155] In the method of the invention, the gas ejection duct 8 with
acoustic treatment is built up layer by layer by repeating the
following steps:
[0156] using the roller 104 to deposit a layer of material in the
well 102;
[0157] locally consolidating the layer by the laser system; and
[0158] lowering the tray 110 supporting the gas duct 10 with
acoustic treatment that is being fabricated, in order to deposit
the following layer.
[0159] Naturally, the present invention may be subjected to
numerous variations as to its implementation. Although several
embodiments are described, it will readily be understood that it is
not conceivable to identify exhaustively all possible embodiments.
It is naturally possible to envisage replacing any of the means
described by equivalent means without going beyond the ambit of the
present invention.
* * * * *